Hey /tg/, could you explain to me why exactly the Craftworld Eldars can't colonize a habitable planet or system and live there? Some Eldars did that, so what's keeping the Craftworld one's from it? I mean it sure seems a wiser idea to settle down in some nice, remote part of the galaxy and actually start rebuilding shit instead of just flying around with no purpose and whining about being a doomed race.
Why would they bother? There isn't really anything a typical planet could offer that they don't have on their craftworlds and it makes them an easy target for any of the various genocidal psychos who populate the 40k galaxy.
By all means, settle down and actually give the other races a chance to finally drive them to extinction. If a Necrontyr dynasty were to find an Eldar populated world, for example, there'd be nothing left shortly afterwards.
If they try to re-populate, they're actually putting themselves in further danger from Slaanesh and her influence, so without a need to expand their population there's no need to give up the inherent benefits a Craftworld offers.
Some fluff mentions Biel-Tan colonizing planets, but they're pretty much the only Eldar trying to seriously rebuild their old empire. The rest ae just trying to survive, and a mobile and highly defended Craftworld is safer than sitting on some random plant. It's not like the Eldar are runnin gout of space on them, considering their population is usually pretty small and Craftworlds are huge.
They would probably get assraped by either deamons, Dark Eldar, Necrons, The Imperium and/or Tyrannids. Not Tau though, Tau are probably Eldar cronies and they're pushovers any way.
Could we reasonably see a Tau/Eldar alliance in 40k?
I hate the way everything is kill the xenos in 40k. In the early days they talked about human/eldar trade and lose local alliances against common enemies. Even today it seems like the inquisition has a quiet relationship with the Eldar.