Anything could be sold out. The popular ammo such as 223, 9mm, 308, etc. will be the first to go, but will also be the 1st to come back. I'm seeing a few boxes of 45 colt ,243, 7mm mag, 300WSM in our local Walmarts, but that is all stuff manufactured pre-panic and just now getting on shelves. None of the ammo makers are going to stop production of 223 long enough to make a small run of 7X57, 6.5X55 or any other ammo that is traditionally a slow seller. These will be the last to get back on shelves after the panic ends.
The only way to make sure you have ammo in stock is to keep enough in stock in your home to get through the dry spells. I reload and have 200-300 loaded rounds of 308 and 30-06 and enough bullets, powder, and primers for at least 2000 more.
I'd buy a SS bolt rilfe of my choice in either 308 or 30-06. Very few come from the factory with irons, but they can easily be added for less than the cost of a budget scope and mounts. Personally I'd just put a quality variable power scope on it with 1X or 2X on the bottom end. I've had more iron sights fail than scopes, a 1X or 2X scope is faster for close range shots than irons and with the ability to go up to 4X- 7X offers plenty of magnification for well beyind 400 yards.
The Ruger All Weather Hawkeye gets my vote for the best buy in this category. I personally prefer the Winchester Extreme Weather. The Winchester is a little more expensive, but worth it to me. A little more refined, slighltly more accurate and they hold 5+1 vs 4+1 compared to most other bolt guns. The Winchester Ultimate Shadow SS is a compromise. Basically the same rifle as the EW, but with a cheaper stock and priced closer to the Ruger.