Will I lose my Sims 4 expansion packs and cc with the new EA app for Windows?

@dramadovey  Yes, the EA App recognizes games that Origin has previously installed.  If you have trouble with this, there are ways to try to fix it, but that shouldn't be necessary.

And to be clear, the EA App should also recognize all your existing purchases even though they were made from Origin.  The game library is shared between the two apps and your EA account as a whole.