I think Vito's plans for his family were pretty straightforward,

Sonny would eventually become Boss of the illegal side of the business,

Mike would oversee the legitimate activities of the Corleone's,ideally under Tom's tutelage.
Public office would, of course, be one of the options that Vito would have supported.

Even though Hagen was not blood,Vito trusted him to serve as Mike's mentor,as we found out when Tom told Mike that he had discussed his future with Vito many times.

Tom would continue to serve as in-house Lawyer/ Consigliere

For Fredo, a low profile,nicely paying career, maybe small rackets (numbers,etc), Mickey Mouse nightclubs,and so forth.

For Connie,cooking, cleaning, and baby production.

Anything is possible,but I wonder how things would have turned out had Vito taken Tom and Sonny's advice on that "Solozzo business"