Add hybrid server for exchange 2010

Hi, 

Although exchange 2010 can support to be hybrid server but it have recommend to add exchange 2013/2016 for the hybrid server. If for short term migration direct upgrade exchange 2010 to latest patch leave is a good choice?

https://docs.microsoft.com/en-us/exchange/exchange-2013-and-2010-hybrid/server-roles

We've need to purchase one a separate certificate one SAN for a hybrid server and a extra public for hybrid mail flow ? The current mail flow can keep unchanged?

https://jaapwesselius.com/2015/07/02/exchange-2013-hybrid-prerequisites-part-i/

Thanks.