1. d.gray-man i could see ending in 5 years or more with it being a monthly series now. could go longer than that.
2. fullmetal i do not see ending anytime soon, which is fine with me.
3. naruto i can see ending in two years, i think the characters have reached their point where the story is at now. once madara is out of the picture and this debate between sasuke and naruto is settled, there's nothing really left. unless kishi pulls a toriyama with naruto and focuses on him when he's grown up and has a family. i doubt it.
4. One Piece, i can see lasting 3 or 5 years more at most, there's still a good amount of material to cover and more to add if need be. i'd be satisfied with that outcome.
5. claymore, not really sure yet.
6. bakuman has two years left. then it's done.
7. bleach. uhhh, i guess if kubo keeps prolonging the whole storyline around a simple goal then yeah, it can go for another 7 years at best. the question is will the material be worth the time used?.
8. tenjho tenge, i'm hoping goes for 3 more years, gotten insanely better in the past two years.
9. gintama can go as long as sorachi-san wants it too. there isn't too many comical manga out there right now. maybe it will go for a complete 10 years.
10. berserk and hunter x hunter, it's unfair to say with the hiatus these two series keep coming across. who knows???.