Hi, and welcome to Grouvee!
Currently there is no plan to change the rating system. There are various arguments for and against a five star system, however at this time five stars is what has been deemed most suitable. The post wheer @peter, the site founder, explains it best can be found here: Replace the 5-star Rating System. It is always possible this will be revisited in the future, but for now 5 stars is the system in place.