It's worth remembering that 9 first team players are out of contract at the end of the season and I'd imagine, of those, only Ralls will be offered a new deal. Whoever is in the hot seat in the summer will need to rebuild the squad, and that will shape how we play and how we move forward for the next 3 or so seasons.
So in that regard, it makes sense to give Morison until the end of the season, and to reassess whether he or someone else will be given that responsibility going forward.
Not that I think Dalman or Tan are smart enough to understand that, by the way. Otherwise they would have given Mick a 1 year deal rather than 2.