hi, as you were using Symbian from quite some time, you know how it performs.android on the other hand is not as good as Symbian except in few cases.it has some problem with the video calling.and it guzzles lot of power thereby reducing the battery life.and it needs lot of resources(that is y it needs 1ghhz processor for proper functioning)the graphics are nice in android.it is an open source software. Symbian was paid until recently.but now Symbian too has become open source.but Symbian is bug free where as android is full of bugs.but the app market in android is amazing.
the future is not certainly the android.it can be anything as almost all the os are open source now.Symbian gives longer battery life and is minimal with perfect features.android is still in its infancy and needs lot of time to get better.
so it is upto you to decide according to your necessity