I agree that this is something only you can determine for yourself.
I personally don't get to go as often as I'd like. Our last trip was June 2013.
We planned for this Oct but it got cancelled. now we're looking at next April.
Am I bummed we won't get to experience TS Island, the train, F!? You bet I am. My son is a train fanatic! I was sooo loooking forward to getting him on a "real" train. We live in Hawaii. We have no trains lol
Will I let it ruin or even cancel the trip? Hell no! There is so much more to do. For us, while there are some things we're going to miss, it's a small amount out of the overall picture of things we'd like to do in the parks. My kids are young (will be 5 and 8) so we still have a ton of things to see and do.
But! that's us. Like I said, you'd have to weigh the pros and cons.