Very less likely.

Vietnam is in very strategic position . Foreign Powers like USA and Russia have more interest in Vietnam than Cambodia.

Vietnam is dominated by east Asian Culture . which is more hard working than Theravada Buddhist countries like Cambodia

Vietnamese are very highly educated and some of them are more fluent in Chinese(both are very effective in Business)

Cambodia economy is based on Agriculture. They employ alot of work force in agriculture.If agricultural product a lone make you rich, Ukraine already been rich which is regard as bread basket of Europe.And you see how bad Ukraine economy is.even though it is in Europe. Vietnam also has large manufacturing base which can diversify their economy easily

Everything is possible but very less likely Cambodia will as develop as Vietnam.