What happens if no one enters a giveaway before it ends?

Pretty sure that even public GA's require at least one entry to receive CV, or you could abuse "broken GA's" (that cannot be entered due to a quirk in the system) by repeatedly farming them.

Will I just get my giveaway limit increased by 1 again and no CV?

No CV even on public ones as no one marks it as received (CV is only given once marked as received).
But you generally don't have any problems with those. A bit more difficult if you have one entry and the winner asks for a re-roll ... I had this recently :-)

I've got similar ones
https://www.steamgifts.com/giveaway/IXiTV/
https://www.steamgifts.com/giveaway/kZX4o/

Creating a post for it is a good idea :)

There's a thread for that: https://www.steamgifts.com/discussion/t3RIy/the-perpetual-i-need-5-entries-for-a-giveaway-thread

You may get some more exposure by posting in this thread.

Edit: Looks like I was too slow in finding the thread :)
Edit 2: You got your 5 entries needed, that was quick.

so my other 200+ entry group giveaway still gives me CV?