Both seem to be possible. But what's their difference?
Instances of the former are everywhere, e.g. a line from 「華麗なるギャツビー」
The latter may be less common (?), but still some instances can be found, e.g. a line from 「賭博黙示録カイジ」
In my mother tongue, which is Chinese, it will sound very weird to use aspect particles indicating progressiveness or continuity (such as 「在」 or 「着」) in such cases. That is, we will almost always opt for the equivalence of 「いつまで待つつもり」:
Therefore, it's hard for me to grasp the difference in nuance (if any) between the two usages in Japanese.