A fair question raymondu
The Oxford English Dictionary online charges $ to use it so,
according to The Merriam-Webster Dictionary online here are your choices.
1 a: a fixed point in time from which a series of years is reckoned b: a memorable or important date or event; especially: one that begins a new period in the history of a person or thing
2 : a system of chronological notation computed from a given date as basis
3 a: a period identified by some prominent figure or characteristic feature <the era of the horse and buggy> b: a stage in development (as of a person or thing) c: a large division of geologic time usually shorter than an eon <Paleozoic era>
Not meaning any disrespect to Red Bull or Vettel, Era's are generally defined in retrospect. 1 b is a good definition in regard to the Vettel/RedBull case. To that definition they may well be on their way.
A little more time will tell.