Back to the OP, I think it would be interesting to set some parameters on what constitutes an era.
In my book, an era is an extended period of time in which one (or more) drivers are the main 'protagonist', who is contested by several other coming and going top drivers. For instance, I consider the Schumacher-era to be 1994 to 2006. During this time, Schumacher was always the main, or one of the main championship contenders. Seven times, he succeeded, and several other times others did, but it was always 'driver X versus Michael Schumacher'. That era in mayor lines, will be remembered as "Hill versus Schumacher, Hakkinen versus Schumacher, Montoya/Raikkonen versus Schumacher and Alonso/Raikkonen versus Schumacher".
Depending on how things develop from here on, this could be the Vettel-era, the Vettel-/Hamilton-era, the Vettel-/Alonso-era or the Vettel-/Hamilton-/Alonso-era. It really depends on who are and will stay the main championship contenders over the next couple of years.
However, if Vettel wins two or more championships in the next 3 years, or two vice-championships and one more championship with no one winning both other titles, and he has thus won 5 (vice-)championships in over half a decade, 2009 to 2015 can be considered the Vettel era. Of course this is just one of several scenario's, but I think it gives a good idea on my definition of a drivers era.