The only way that the SPOe redeem themselves is if they increase immigration levels; people are probably unhappy with the centre-left because there hasn't been enough immigration.
You're partly right. The solution to the "problem" of immigration is to draw in more immigrants and naturalize them, so as to drown out the racist vote. This strategy is already starting to pay off in the US. I wish Europe was smart enough to follow suit...
As for the poll question, in case of a tie I always bet on the worst outcome, so FPÖ.
The SPÖ cannot naturalize foreigners on their own. That's the responsibility of the Interior Ministry, which is in ÖVP-hands.
Besides, it's deeply disturbing that you advocate naturalizing foreigners only for the purpose of winning elections for center-left parties. If they have to rely solely on this to win, they are politically bankrupt because it shows that they have no solutions to actual problems ...