He is now close to top 20 without playing his best tennis.
I think the max ranking for Gasquet is top 15,
he is very talented, good tennis but nowadays the most important weapons for a player are the physical and the fighting spirit, you don't need to produce a high sophisticated/technical tennis, a basic style tennis ( good serve and solid defense on the baseline )+ good physical and mental/warrior style are enough to be in the top 10,
Gasquet doesn't have a solid physical, he is often injured, he seems to choke during key points and he has difficulties to win against top 5 players ( the psychological barrier is too high for him ),
that's why I think Gasquet can not be in the top 10, he can win one or two big tournaments ( ATP500, maybe a masters 1000 if he is lucky with the draw ) but win a grand slam seem to me an utopian view,
he is a good top 20 player and I think Gasquet will be happy to stay top 20