It is hard to believe Vince would have been a legit threat to end The Streak, although with heavy promotion and a variety of storyline props (Taker injury, crooked ref, outside interferrence) the booking might have been good enough to keep you interested.
I do give Vince credit, he is not a wrestler, even in the part time sense, never has been, never will be, he does play a great heel character on TV but the character, although a very effective villain, isnt a wrestler. It takes a lot to get Vince in the ring, but when he does he is also smart enough to book short matches that stay competitive without being unrealistic, staying true to the sneaky, heel nature of his character, but always ending in his opponent getting a clear cut definitive win, which is EXACTLY what the audience wants. Whether it be Hogan, Michaels, DX, Flair, etc, Vince doesnt embarrass the real stars by booking himself over them, or infuriate the crowd either.
As for Vince-Taker, since they clashed in 2003 on PPV a WM showdown seems unecessary. Vince-Hogan for example had never happened and it had a built in storyline (Who Made WWE). As with any Vince or Hogan match you didnt get a classic but they kept it believable and Hogan triumphed clean in the end, which we all wanted to see anyway.
The Streak itself was never even mentioned until WM 17. Only after beating Triple H & Flair back to back did The Streak itself start to become a storyline prop. At that point, with The Streak playing g key role in Taker's WM storylines, even with great booking I dont think Vince would have been a good choice as an opponent. At least through last year there was legit chance that Taker's Streak could end as he battled Orton, Batista, HHH, HBK, Edge, I think a Vince match would not have been recieved as the same level legit threat to the Streak.