If you can sell anything for more money than you have in it....sell it. I have made money buying and selling when the market is like it is now, and I have made money buying and selling when 400lb black steers brought $1 a pound, and great cows could be bought for $800. Your money is made or lost on a deal when you buy it. Doesn't matter what the market price is, as long as you pay less than that when you buy it.
I think that people who sell out now, will be better off, even if the prices are still high next year, than people holding on to them thinking they will be higher next year. I wouldn't worry that you might not can find the cows you want when it is time to buy back. You will be able find them