Just wondering if both Standard and LImited Membership allows using this?

I still want to be able to post my WL Multiples, as well as shop other people's lists. 

Yes, both of those membership levels allow access to read and post in forums. 
It's just the a la carte members that will have read-only access.
 

If I don't upgrade to a pay membership by the 15th will I loose my wishlist and have to start over when I do buy membership? I plan on buying one in time, I just was wondering in case I don't.

No, Alexandra, you will remain an a la carte member by default with 100 spaces on your WL.  All of your current WL books will remain on your list, but if you have over 100, you won't be able to add any more until you are under the 100 allowed or you pay for a membership.  Have you seen the thread in the Book Bazaar where you can give someone 6 or 9 credits (depending on if you want a limited or standard membership), and they will purchase the membership for you?

Thank you. My wish list is currently full with 200. lol. um. I didn't see that, thank you. I currently only have 8 credits. darn 1 short.

Alexandra...I'll gift you one more credit so you can trade it for a membership if you want.  If you don't use it for that I won't be offended though. :)

for  Shelby!!