When do journal invitations for computer science conferences typically come out? In some computer science conferences, a few top papers are invited to be published in a special issue in a journal. I have a paper to be presented at a conference soon and am thinking of submitting it to a journal after that. Roughly how long should I wait to make sure that I don't miss the opportunity in case my paper gets invited to a journal?
In my experience, this varies widely, even for different iterations of the same confernence.  Sometimes invitations go out two months before the conference; other times they go out two months after the conference.

Write the PC chair and ask.  Unless you have good reason to believe your paper is likely to be invited (based on the reviews or other feedback, not just your own personal opinion), you should probably ask when and how papers will be selected, not whether your paper is being invited.