TPG (thepointsguy) is reporting a new offer of 50k after $750 spend for the regular Hilton AMEX... link is on his site. Clicking through to the application shows that it expires after 2/28/13 as well.
I applied for the Hilton AMEX yesterday without checking here first and got approved for the 40K after $750 spend. Has anyone had any luck getting AMEX to change the promotion from 40K to 50K, or something similar, after you've already been approved?