I don't think they're going to make it - the next federal elections are in September, that's much too soon to jump over the 5% hurdle. But any votes they get at all, will decrease the votes for the current coalition partners CDU/CSU and FDP; a center-left coalition of SPD and Greens would be even more likely to bail out other Euro countries.
The
latest polls put the current coalition at 46%, and an SPD/Greens coalition at 40%, with the Left party at 8%. Other small coalitions, like the "Jamaica" (CDU+FDP+Greens) or the "traffic light" (SPD+Greens+FDP) or SPD+Greens+Left are not feasible (yet) at federal level, though they have been realized at state level. The only alternative left then is another grand coalition of CDU and SPD. The great disparity in size might make that actually much more difficult to realize than last time.
And as you see in that poll, the FDP barely is at the 5% hurdle. Whenever that was the case in past elections (at least since the days of chancellor Kohl that I'm aware of) the CDU has actually encouraged her voters to vote FDP to keep them in parliament: when, say, the FDP only reaches 4% those votes are lost and the CDU can kiss a chance at governing without the SPD goodbye. And indeed, in those cases, the FDP had a big upsurge in the actual election results compared to the preceding polls.
I expect the same to happen with this "Alternative for Germany" party. The CDU will appeal to their potential voters not to throw away their vote and jeopardize that those left spend-thrifts come into power. Or even more likely, the FDP will try to appeal to those voters taking a stance too of "not a cent to southern Europe", and then after the elections completely forget about it and play perfect lapdog to the CDU once in government, as they've done every single time before.
