Avatar won't spawn anything lasting because it can't. It was written as a one-off piece that doesn't stand up to reflection.
Your definition of 'spawning anything' seems to mean spin-off material, like the reams and reams of stuff that Stargate had. I think it can be safely said Avatar
will have a sequel - this has been
confirmed - and it may have other spin-off stuff. Like a third movie. Which would be enough. We'll see how viable the Avatar brand is, but frankly it's reached a success that Stargate in its almost two decades of existence could only dream of.