EA owns the rights, and are not likely to relinquish them without an unreasonable sum or some horrible arm-twisting agreement.
After the first Spore, they're not likely going to take that risk again, not when they can pursue other more successful game series (or just follow the usual gaming trends).
Spore 2 could work, but it would really have to be under a different name, and a different leadership to truly work. As much as Spore needed the simulation aspect, it also heavily needed the involvement aspect that can't truly be given in a game that amounts to a vivid skin pulled over a framework skeleton. When you look at it, the Sims has always been a rather skeletal system but padded with charming feedback and polish. It works because we can narrate our own story between the lines. Spore couldn't work like that, as we are creating and learning entirely new stuff as we go along. It isn't enough to assume some will narrate their own story between the lines, the players themselves want to be directly stimulated with a less pre-meditated, heavily restricted system, and tinker with the outcomes. Maxis specialises in 'dollhouse' simulation, and Spore was beyond that scope, though perhaps they could have made a mean Tribe or maybe Civ stage. The creature phase, I think, was one of the most anticipated aspects of the game. Just the first-hand exploration of an alien world, with that degree of creativity, was a huge selling point for most. Just that phase done well enough could be a colossal success, but finding the sweet spot would probably be hellish.
There is a gaping lack of games with an emphasis on freestyle creation (that has a real impact), and the ones that get it right, are often shunted forwards to sleeper hit / cult idol status. As it stands with the current technology, it's too much of a risk of time, money and manpower to delve too far into. At least when the staples of generic gaming are right there and waiting to be milked some more. Eventually, yeah, we'll see slivers of the game we all wanted elsewhere, but right now, nothing seems to be on the horizon.
