Sorry, however, SF will keep their two seats in EP.
They should hold their Northern Ireland seat certainly.
I think, at this point, that they'll lose their Dublin seat. Dublin is being reduced to a 3-seater next time, and SF just won't get a high enough 1st preference share or more importantly, enough transfers to be genuinely competitive. If the result in Dublin is anything other than 1 FF; 1 FG; 1 Lab then it will be somewhat surprising.
Maybe,
just maybe, they can gain 1 in the North-West constituency. But it's too early to say - depends on whether or not Harkin runs for re-election and who else decides to run. (There's certainly 1 FF; 1 FG - the other seat could go in a number of directions).
As it stands, they'll certainly take 1 and are competitive for another, but I certainly don't think that anything so definitive as your statement can be made.