I feel this is the First small car that GM has brought to the US market where the Name will be carried on for several generations, in the past the created such one hit gems as, The Vega, The Chevette, The Metro and The Aveo. None of these cars really had a positive buzz about them, so there was no desire for the names to carry forward. If Chevy keeps the Sonic Quality and Value going there is no reason for them not to want continue using the Sonic name...
Usual age age 3 to 6 years. Refreshing at the fourth year will last thru six.
Biggest exception to prove the rule: Corvette which can go for almost a decade for an iteration.
Based on EPA classifications, the Sonic hatchback is a midsize.