Yep, I had that offer to upgrade my PRG to the Platinum for a long time too, and as much as I wanted a Plat with the amount of travel I do (weekly) I waited until that last 100k bonus came along and jumped then.
Incognito browser until you find the 100k... then close PRG.
I always have the upgrade link.
I actually tried incognito and the current offer is 40K
I had the upgrade offer, used chat to see if there were any bonus points offers and of course there were not.
I did the math, read this "10 Things to Do When You Get Amex Platinum" article on TPG, and decided to just "cold" app for it with the 40k bonus. Instant approval, card delivered first thing Monday morning, and I'll start working down the benefits. I'm already SPG gold organically, and Hilton gold through Founderscard, but the car rental promos and lounge access (and $200 airline credit) will make it worth the annual fee at least for the next 2-3 years.