WoW is almost certainly getting new races in the coming expansion. They want these races to be able to sell expansion boxes, after failing to include anything for players who are not at least at least level 55 (if they want to re-roll Death Knight, 68 if not) in the current expansion. Look at Penny Arcade's famous take on Blood Elf racials if you want some idea of what to expect.
Meanwhile, SOE is in the process of nigh doubling the number of racial tradition choices in EQ2. The current number is way too small - if you didn't choose one of your race's favored tradeskills, you can already collect ALL of the other options.
I group these two changes together because both are things that are being added to the game that have a RELATIVE effect on existing characters.
As far as I am aware, there will be no specific nerfs to the non-Goblin/Worgen races in WoW. EQ2 is undergoing the process of consolidating its critical strike/heal/spell stats into one universal number, as WoW did in Wrath, which will affect some existing racials, but there's no reason to believe that the existing choices will be getting worse.
In absolute terms, if you did 100 DPS before the changes, you should still do 100 DPS after the changes. In relative terms, though, your existing character might be less appealing when the dust settles - perhaps a new race does 102 DPS, or has some killer PVP special ability, or perhaps you just really love Goblins and would have chosen that race just for the looks.
The Role of Race in MMORPG's
I would not consider race to be a fundamental aspect of either WoW or EQ2. Your faction may determine which NPC's are willing to talk to you, but each of the sides has approximately equal numbers of NPC allies. If Blizzard swapped out my gnome mage for a human one, I would be puzzled by the change in character height, but it wouldn't make any difference in my actual gameplay. If they swapped it out for an undead one - an upcoming paid account service - I would need a new guild, and would need to figure out where the Horde's NPC's live, but, again, minimal impact on my gameplay. By contrast, I'd be in for quite a learning curve if someone swapped the class of any of my characters.
The quirk to race is that it is one of very few things that affect your character but cannot (yet) be changed. If Blizzard nerfs my Arcane spec, I can switch to a different spec. If Blizzard nerfs my racial bonuses, I'm stuck with a decision that I might have made differently, had I known that it would happen when I rolled up the character back in November 2004.
There are good lore reasons, to be sure - you can't really turn a 30 year-old-human into a hundred-year-old-elf in most settings. The system also has some flavor benefits. Perhaps I would like my EQ2 ranger to be a Wood Elf - the only race with a racial bonus to bows. Perhaps I would like the challenge and uniqueness of playing some combination that is not really all that supported by the stats, like an Ogre caster or a Ratonga tank. However, it's not a choice if the change that makes Dark Elves into supreme rogues and Erudites into the optimal casters goes in AFTER I made my race choice (which, I'm told, is precisely what happened to EQ2 players who started before the current racial system was implemented).
What should players expect?
Everything in an MMORPG is subject to change, and has to be subject to change. Bugs and imbalances need to be fixed. New content and options need to be added to keep the game fresh. Obviously, it would be nice if developers made an effort to be as value-neutral as possible when messing around under the hood, but it is not realistic to demand that any portion of the game can never be changed.
That said, because race is not such a fundamental part of the game, I do think that players should have the option of changing their race when significant changes are made. The player with the character in question legitimately leveled that character at some point; if anything, the effort they invested back then might be greater than the effort that would have been required to re-roll today. There is no question that the character might not be able to function, the way there might be if you changed classes.
Of course, players who are dissatisfied with their race choice could always re-roll, but the very nature of the persistent world MMORPG is designed to encourage attachment to characters. It's easy for someone who is still happy with their current choice to say no when other players complain that a patch made their race obsolete. If the next WoW or EQ2 expansion introduced a version of DDO's 32-point characters (which are superior in every way to default characters, but must be unlocked through gameplay on a character who will not be retroactively upgraded), they might take a different view.
A transaction I can support
Overall, I think this is actually a good place to implement paid account services, even though I generally distrust the effect these transactions have on the developer's financial incentives.
Either racial benefits play so small of a role that there won't be any demand, or they are significant enough that players should not be stuck with the effects of changes they could not have forseen when they made their characters. In either case, it will very readily become apparent if the developers start making a point of making a different race overpowered each patch in the hopes of selling more race changes.
Sure enough, SOE is waiting until they finish the racial revamp before introducing their race change service, and Blizzard is restricting their faction transfer service specifically to prevent characters from changing races within their own faction (even if they transfer and then transfer back - a restriction that I personally think is largely moot). I'd expect that even the most desperate studio understands that gutting and overhauling the racial system is a card that can't be played all that often, and that players will expect races to remain reasonably close to their current abilities.
I admit that would be unfortunate if the first level 80 Worgen/Goblins were leveled up on the opposite faction before the expansion, for immediate transfer on launch day. Beyond that niche case, though, I generally think that the benefits outweigh the drawbacks.