I'd like to see them keep it only server based though. It would promote the community more and help weed out capable vs incapable players.
I'd personally place a higher priority on features, tools and content escalation that teaches the incapable how to be capable, as well as fosters a mindset encouraging that sort of inclusion rather than fixate on only that which segregates the 'capable' from the 'incapable'.
I say this for several reasons, chief amongst them being that if you'd like to see a massively negative community that is rife with fixation on its segregations and factors for segregation and stratification of illusory 'ability', you need look no further than trade chat in WoW.
Just pick a server and go hang in Orgrimmar or Stormwind. A half hour later and you'll probably have a pretty fair idea of what we don't need to be replicating.
Mindset is important. The tools and features available as bridges into escalating, capability-demanding content need to be accessible and they need to work in a manner that, if nothing else, isn't directly damaging to the whole concept of a raidgame's mindset.
I've ranted about it elsewhere, but the reality is, TOR's trying to be a raid game. If they want to replicate the toxic community standard of WoW, they need to do nothing, as that toxic, negatively steeped 'community' divided itself viciously across all kinds of imaginary lines, and no small number of those lines formed between those that got to do the dungeons and raids regularly for having access to, typically, a functional (if not always healthy) progression/raid guild...and those that, for whateve reasons, could not or would not.
THose that did not often wound up on one side of an ubiquitous fence and essentially became the spat-upon inferiors. Inspects and armory data, then gearscore, then item level succeded, in addition to their intended purposes, in widening the rifts and turning smoldering resents on both sides into raging infernos of interwebz hatred and disdain.
That war of sorts exists here as well. You need look no further than elsewhere on the forums for the threads about add-ons to see a spill-over battleground.
The problem never really was intra-server crossover in the dungeon or raid finder.
The problem never had anything to do with the actual difficulty of the content.
It had everything to do with the accessibility of said content and the mindsets that evolved on both general sides; the Haves and Have Nots, so to say; and all the things they respectively blame for all their perceived woes.
Mindset is important. So important, in fact, that fostering the desired mindset really ought to be a primary concern for the dev team, though I suspect my posulate there is quite possibly way ahead of its realistic time.
For a realistic basis of expectation, expect TOR to feel a lot like World of The Old Republic-craft with laserswords in short order. Except not so savvy to the macrosocial and psychosocial requirements of such things, or finesse in crafting and scaling the content on par with Blizzard's...possibly ever.
Reality kinda sucks, but as far as I have cause to believe at this time, that's my prognosis.