We already have two developing QB's as our #1 and #2.
The only way White beats out Grossman was to outplay him. White showed some useful signs but he didn't come close to doing that. He's a much better runner than QB right now.
I agree totally with this. The traditional "developmental" third QB is generally in place when you have long-established #1 (and often #2). I actually think we'd be better served with Rex's experience and steady (and well-liked) demeanor than Pat White's inexperience and need to learn. I might have thought differently had White clearly outplayed Grossman, but that's not the case.