We must remember too, that stealth coatings and materials are fragile. Not as much as in the past, but it wouldn't be a stretch to say that even if the airframe can go past M 2.5 (which is highly probable), the coatings will just strip off. The plane can go that fast, without doubt. Is it worth it, ie. will the plane have enough stealth afterward? Maybe not. Which is why this wouldn't be used as a tactic, more like an emergency capability.
"Like the coldest winter chill, heaven beside you...hell within" Alice In Chains