Hmm... sick of defending a valid theory. Well, that's how theories go. If you propose the theory, it's up to you to present the evidence, and defend it.
For instance, I have a theory that the Ayleids are coming back. I base this on the fact that they left the water running in a few of their ruins, and the turned the security systems on before they left. Why turn on the security if you don't plan on coming back?
Anyway, for the sake of argument, it is entirely possible that in some future game, the Dwemer will return. How? I don't know, I'm not a writer so I'm simply not that creative, but they wrote the Dwemer out of existance, it's only a few flicks of the wrist to write them back in. As such, all arguments seem to be capable of being valid. The simple problem here is that most of the evidence we have concerning the disapearance of the Dwemer is anecdotal, which is simply unreliable, even when coming from a God, or from the last remaining Dwemer. The Dwemer were many, then all of a sudden, they were all but gone. They haven't been back, and nobody has heard anything new about them. A reasonable person would simply accept these facts as truth, and determine that they're gone and won't be comin' back no more no more.
Yet, the fact that there IS one Dwemer remaining allows for the possibility of more Dwemer remaining, somewhere, perhaps EVEN in a large colony. Of course, there's no evidence for such a proposition, so anyone who claims that this is the case is likely to have their theory torn to shreds.
So, basically what I am saying is, theorizing about lost colony's of Dwemer is kind of like theorizing about Alien Abductions, Monsters, Ghosts, Gods, Demons, Unicorns, Bigfeet, Tasty Vegen Food. There's lots of personal accounts, but where's the beef? If you have a theory, you'll simply need to present real evidence. To answer the OP's question, no, there's no historical evidence that there's a possible lost colony. While that doesn't mean that there isn't one, a reasonable person would assume that this is the case, based on the fact that for all their searching, no evidence has been found.
On a side note, it's cool to see some old-heads in here. Everyone in Oblivion forums seems to have joined within the last 6 months. And they can't spell, and I don't mean in the typo swnse, I mean in the ratardid cents.