Hello Timing of Surgery depends on requirement of Patient. If you feel difficulty in performing routine activities then go for surgery now else wait Having said that it is provisional diagnosis. Kindly follow advise of your doctor

Till you enjoy useful vision with specs ,you can avoid the surgery. But if there is no improvement with glasses then you can get the operation done ,preferably by an experienced surgeon,and at a place where all tertiary facilities are available.

Cataract formation after a retinal detachment surgery could be due to the silicon oil which is used during the procedure and /or after vitrectomy .Commonly that does happen.Still the decision of cataract surgery purely depends on the decision of patient and the treating surgeon.If the surgeon is competent enough to manage any complications and the severity of vision loss is profound then I would suggest a surgery.Frankly speaking your case is not meant to be managed by a novice surgeon and it carries a greater degree of risk involved.