It's going to be unusual ... assuming Bernie doesn't pull off the mother of all upsets in Wisc NY and CA .... and assuming the gop doesn't somehow deny Trump the nomination. All conventional wisdom is the senate is the dems for the taking .... so long as whomever they nominate wins or at least wins in enough battleground states where the gop is defending the senate, and despite Hillary being toxic outside the party, assuming she can get the Bernie vote, she should win because Donald will have blacks and latinos and Asians turning out in record or near record numbers.
HOWEVER, given that we know Trump will say absolutely anything about anyone regardless of any lack of factual basis or even borderline human decency, and God knows Hillary's pulling freight cars of baggage, it could be that Trump can run a campaign for next to nothing, burning the national landscape behind him for the gop, and force Hillary to spend a billion dollars leaving the dems little to nothing for the senate.
The irony is that in many ways, Bernie's a better candidate, but he can't seem to get blacks, and most latinos, to vote for him against Hillary. They'd still vote for him if he were running against Trump.