Restored a new MacBook Pro from TimeCapsule and now it wants to create a new sparsebundle when backing up
Normal and expected. You have a "new" Mac that has not ever backed up before, so it will make a new complete back up and then continue to back up incrementally after that.
I have about 2 years of backups, that I prefer not to lose.
You won't lose anything. You will have two sparsebundle files on the Time Capsule now......one for the "old" backups and another for your "new" Mac. After a few months or so, you might decide that you really don't need all the old backups going back months and years. If that is the case, you can simply delete the "old" sparsebundle file to clear up a large amount of space on the Time Capsule for new backups going forward.