The reason Andorra is not coming back is because they don't have the money. They were even going to leave the EBU altogether as even EBU's fees alone were becoming too much. So I'd doubt it'd make much of a difference.
That is true, they need to promote themselves. If you go around the streets in Portugal and ask people how many countries exist in the Iberian Peninsula everybody will answer 2. Then you say there's 3 and they'll be like "Wait what?"But Eurovision was quite important for them, even if they never got good results. I mean, it's promotion for the country. A country that many Europeans don't even know where it is. And tourism (and washing money) is their main economy.
Anyway, they said they were going to take part once in 2-3 years. Already five years they're out. I think they will come back any moment soon. And of course if Spain, France or Portugal win, that would help a lot