In Diplomacy, will I be "cornered" as Turkey if I don't use the "juggernaut" opening?
Well the answer to the question literally posed in the title is yes. You can be boxed in, but this will not necessarily happen. Hey, even if you do ally with Russia, Austria and Italy can put up an effective blockade keeping you in the corner.

It is certainly a viable strategy with significant growth opportunities to ally with either Austria or Italy. (Maybe you really should be asking Don Scheifler and not me, since he soloed as Turkey off the back of an Austrian-Turkish alliance at the recent World Championships).

The key, as always, is to try to keep your growth paths open while keeping your allies busy so that they can't afford to stab you. Of course the other six players are trying to do the same thing...

To look at the particular senario you bring up of an alliance with Austria. OK so you've got the Russian neutralised and say picked up SEV in the process (which is a great longterm gain), then barring western intervention (and this is the key), you and Austria are favourites to roll through Italy. Yes a stab is a risk, but this is the case in any alliance. Arguably an Austrian stab is less likely to be devastating than a Russian stab, since under normal circumstances Turkish home centres can't be taken without fleet power which Austria is unlikely to posess. Just keep your ally busy and then they won't have the units free to stab you (or you could be the stabber).