I think if you take the long-term view, Olli would be better off spending one more year in the minors. Odds are he will not be this much of a standout as the season wears on, and Jacob made a good point in the other thread that frequently rookies who stay up struggle more as the year goes on. I think that's particularly true of D and G.
Also and equally important, given our depth in WBS (Despres, Dumoulin), there's no shortage of guys who are ready and physically stronger than Olli, who can take over in the event of an injury, etc. I think Olli has been great and part of me would like to see him stick but he's also got to be very confident right now, and sending him back in that state of mind, ready to win a full time job next fall after FA shakes things up a bit... is better than risking him starting to struggle and sending him back to London in that state of mind.
Have to go with the odds, and the odds are, he won't be this big an impact all season. But very excited to see what he can do next year.