I doubt it makes a great deal of difference. Serbia is probably going to be defeated a few months earlier and a dozen or so Austrian division freed up for use, probably on the REussian Front. Irtt seems unlikely it will make much difference but it will boost morale in he Central Powers.
This could snowball into something substantial. If it appears that Serbia is going to lose soon it will likely entice Bulgaria into the war much earlier to grab Macedonia. Assuming OE still enters the rail line to them will be open for munitions which very probably does away with Gallipoli.
Freeing up AH divisions to counter the Russian fall offensive could be huge if the second siege of Przemysl is avoided. Then you avoid Conrad's extremely costly winter offensives trying to save the fortress before its food ran out.
