IF you subscribe to the premise that all realities exist at the same time side by side like Doc Brown said in Back to the Future 2, then here is what I think.I wonder if they will address what happened to those they "replaced", ie, the other Henry.
It stands to reason that if the people that time traveled to 1947 and then came out in this new reality ( eureka of this season) , then the people from that reality also time traveled to 1947 and came out in the other reality( the eureka of last season)? Maybe a cross over parallel dimension ala "SLiders" is in order to get everyone back to their own reality.
But I am betting if that happens it would be really weird with two of everybody existing at the same time. Also would the black lady with the boy that is autistic want to go back to her own reality and deal with the autism issue again?