Air to Scandinavia (Stockhom) and back (Bergen) to East Coast

The fact that SAS is moving to Skyteam may eventually mean schedules and
fares may change, but they do so all the time anyways, so I don't think it is
a meaningful concern for you.

You won't get a nonstop flight from Bergen back to the US on any major airline
(I haven't checked Norwegian or Norse). So you will most likely have a
connection somewhere in Europe, and wherever that is, it will most likely
drive your outbound airline choice. If you take the train back to Oslo (which
is a beautiful ride anyways), you will get more options.

You say nothing about what your preferences/requirements are. Cost, premium
seating, lounge access, airline alliance, etc? You may get more input if you
add those parameters in.

Where on the east coast? SAS and Icelandair are possibilities. I’d just get on googleflights and see what works from your local airport.

SAS is moving from Star Alliance to SkyTeam so you may have more options next year if Delta flies out of your local airport.

In general, SAS is a good option between North America and Northern Europe. Air France-KLM has bought 20% of SAS but I can't see why that would have a large impact, the only difference for passengers is that SAS will leave Star Alliance and join Skyteam.

It really depends on what hub your flying out off - NY, Boston, Atlanta, etc. That will drive available airlines and flights. We usually use Atlanta where Delta, AF, KLM, and now SAS have flights to Europe. The transatlantic flights are usually 1 airline going and another coming home but that is because we don't fly round trip.

I'm in PA, and for the Scandinavia tour last August I chose to fly PHL to London round trip, and took separate trips (not the same day as the London flights), to Stockholm and from Oslo. I was interested in spending a few days in London, which may not be your choice, but you could do something similar with another city.

Many thanks to all of you. I was concerned about the sale of SAS and if I purchased tickets before the sale and what might happen later, after the sale. The types of seats and availability on SAS is looking to be the first choice.
Thanks again!

I was concerned about the sale of SAS and if I purchased tickets
before the sale and what might happen later, after the sale.

The sale happened last year. And the only impact I can see happening is your ability to collect frequent flyer points on other airlines from the flight.