It really depends of "X" number of factors. Such as how your script is optimized as first, is this going to be 10k in an hour and then nothing, or spread across the day... Really a lot of variables there. If you could provide us more details we might be able to help you a bit more.
In some cases 20k can be put on shared hosting, in some cases even 1k visits are more then enough and eat up resources available.