Of course, bombing campaigns sometimes work. For example, it worked fabulously in Libya. What the US et al need is people on the ground to mark targets and for indigenous ground forces to press home the advantages created by a bombing campaign. Both those conditions were present in around Kurdistan and IS was pushed back there.
Now, however, badly lead the Iraqi army is, there is some reason to be believe the Iraqis could successfully drive IS back from Baghdad. The question is who to partner with in Syria. The US is pushing the Turks to fulfill that role, but I doubt Erdogan will bite. He has staked far too much on regime change in Syria. Indeed, according the Seymour Hersh, it was the Turks that supplied Syrian rebel groups with Chemical weapons in the hopes of goading the US into bombing the crap out of Sryia. You can read the article here. That said, there is hope that the US can put enough pressure on Turkey to prevent it from becoming to IS what Pakistan, the ISI in particular, has been to Taliban. Up to this point Turkey has been a jumping off point for Jihidi tourists, the primary destination for illegal oil transports and a major source of funding.
Kobani may be a game changer for a number of reasons.
1) If the city falls and IS does its worst, the Pesherma may reconsider its unwillingness to press beyond the Kurdistan.
2) In Turkey, both internal and external pressures will increase exponentially. Conservatively the number of ethnic Kurds in Turkey is around 10 million.
3) There will be a great deal of pressure on the US to step up bombing. This in turn may prompt other rebel groups within Syria to A) distance themselves from IS to prevent from being targeted and B) offer to aid the US campaign for their own purposes.
4) Although the Syrian regime helped spawn IS (see Hersh again), the regime is in many ways a natural partner in the fight against them. A massacre in Kobani may make cooperation, which has hitherto been unthinkable, possible - albeit on a convert level.