It's unlikely that the new airport will be operational by then. I would make any plans based on the assumption that the old one is still being used.

For bags, I would assume that it depends entirely on if the check-in agent at your point of origin is willing/able to check the bags to the final destination. That has worked for me before, but I have never tried to do this through DOH specifically, nor with your specific airlines.

In case they are unable to to check the bags all the way through, I would factor in an overnighter, because you will in that case anyway need to buy a visa (assuming your nationality allows on-arrival visa, of course) and then take a taxi from the arrival terminal over to the departure terminal. You might as well let the taxi take you somewhere else.