Well, allowing for another one or two filler arcs, and assuming that the manga ends anytime soon (which it may or may not... who knows at this point?), then I'd say somewhere between 200-225 episodes. I'm actually hoping it's not much more than that, because I don't want it to drag on too much, and it's already starting to show slight signs of doing that. Mostly it's that filler again, but still... I don't want it to turn into Inuyasha Z or something. XD
::Naraku and Inuyasha face off for twenty episodes::
Naraku: ::power level 1000:: Kukuku, Inuyasha... you'll never be able to defeat me.
Inuyasha: ::power level 1000:: ::thinking:: 'He's right... we're evenly matched!'
Everyone else: ::on another planet waiting anxiously:: Gee, I hope Inuyasha's all right!
Inuyasha: 'I have no choice... everyone, lend me your strength!'
Naraku: 'What is he doing...?'
::Naraku watches curiously as Inuyasha spends another 20 episodes gathering all the energy from everything into his spirit bo... er... sword. Not THAT sword. XD You know, Tessaiga::
Inuyasha: ::power level 1,000,000!!:: Now I'll finish you off once and for all! BAKURYUUHA!!!!
Naraku: :ph34r: 'Where did he get such power....?!'
::Naraku dies and stuff, but then the planet blows up too, conveniently::
Inuyasha:
Everyone else: Nooooo!THE END (Except it's really not, because the show actually NEVER ends)