That is actually quite a silly statement, its like saying if B&M REALLY wanted to design a train for one of Intamins monorails, the COULD.
Its kind of obvious that a roller coaster manufacturer would be able to design a train that is capable of running on a different track gauge, although I doubt that Maurer would one day come out and say 'You know what guys, lets give up making track, lets just make the trains instead'
Manufacturers designing trains to run on existing rides is different, because that generally improves the lifespan of the coaster, makes it more efficient and less maintenance.
Why Intamin would ever design a coaster and then give Maurer a call and say 'Do you mind if we borrow a few X-car trains, we can't be bothered to design one for our own track.'
Intamin would be perfectly capable of designing a train to run on their own version of an XCar ride type if they wanted to.
On another note, I cannot see Drayton thinking 'Lets get a new Intamin for 2010, but since its so expensive, lets knock down G-Force and keep the trains.'
We could sit around making stupid predictions about the future designs of some of the most reputable ride manufacturers out there, but since we know that anything is REALLY possible, it doesn't mean that it would ever happen.
B&M COULD design a coaster track for Intamins Zac Spin cars if they REALLY wanted to.
S&S COULD design a track for a Mack Wild Mouse car...
They just wouldn't.
Gerstlauer COULD create a track to run a Maurer Spinning car...
I could go on and on for the rest of they day if I REALLY wanted to, but I won't.
I can't see where a manufacturer would ever want to design a steel coaster track to utalise the trains off another company when they still make their own rides to run the trains.