You may or may not gain weight, but there are other considerations at play. Excessive caloric intake will probably cause you to gain weight, plus there are other metabolic considerations from the reduction in exercise that may have an affect as well.
When you have an excessive amount of protein intake, then you start placing a larger burden on the liver (deamination of the proteins) and the kidneys (excretion of the excess ammonia converted to urea), as well as being converted to glucose and ketones in the body.
It can have an affect on blood acidity, which in turn can cause calcium loss as the body tries to normalize blood pH.
If you can't exercise for a period of time, I would reduce all your macro-nutrients in proportion, then resume your regular diet when you can get back to full activity. There have been a few questions on the site on how to start back after a period off, as your strength and conditioning will fade a bit.
While it is a very general rule of thumb, personal observation and kinesiology classes that I've taken suggest that most people are ok with up to 7 days being off and having minimal losses. After that, it will take two days to gain back for every day you were off. Some people have greater losses, some have less, it all depends on your body.