Your version doesn't work as advertised here. I reckon you need '|' (bitwise OR) instead of 'Or' (conditional OR).
Last I checked, "here" is a Blitz3D forum: And, Or, and Xor are bitwise, and Pipe is not an operator. Seeing that there's a Strict pragma in (what I assume is) BlitzMax is making me want to switch though!
I really like NextPowerV2(). It's both simple and cute. :)
If you're concerned about speed, I would suspect a binary search in NextPowerV3() would prove faster - even if you want to weight it for a particular range, it'd still be faster to cut your potential answers in half each guess instead of guessing arithmetically.
Personally, I would find that function much more readable if the hex notation of literals (e.g. $2000000) was replaced with "1 shl 27". I would assume either compiler would optimize away simple, constant mathematical expressions before runtime.