I think you saw my post on the updated PRG/Gold Card this morning, with links to DoC's writeup and the reddit discussion about his post.
https://www.disboards.com/threads/i-love-credit-cards-so-much.3528202/page-2579#post-59769801
This is supposed to be a revamp or rebranding of the Premier Rewards Gold card, not an introduction of a new card product. The new benefits leaked online early, and were promptly pulled back this week. However, the new benefits are supposedly rolling out on or about 10/4/18. Because this is an update of the PRG, existing cardmembers will get the new benefits the same as new applicants who apply on or after 10/4.
Offhand, the two differences that I see between applying before or after 10/4 are:
(1) If you apply before 10/4, you'll get the current plastic card; whereas new cardmembers on or after 10/4 would probably get the new metal card in Gold or Rose Gold. Again, the rose gold color and metal card design are rumors, but it'd be pretty exciting if it's true. If the new PRG/Gold Card does become available in a Gold/Rose Gold metal design, it's likely you can just call into Amex to request the new card (just like how they let Platinum cardmembers call in to request the new metal cards when they first came out).
(2) The rumored public offer on the updated PRG/Gold Card is supposedly 25k MR after a $2k/3 month MSR, with up to $100 back in statement credit on restaurant spend. The best targeted offer currently on the PRG is 50k MR after a $1k/3 months MSR, which might be available under your Amex pre-qualified offers or on CardMatch. You can also pull a 50k MR after $2k/3 months MSR pretty easily in incognito mode (just keep trying using different browsers). I don't think anyone knows if the higher 50k MR offers will be available on Amex, CardMatch, or in incognito after this card is updated. For those who value an extra 25k MR more than a possible $100 statement credit, they're jumping on the certainty of a 50k MR offer by applying before 10/4.
You can’t combine MRs between spouses or within households, but you can transfer MRs to another person’s frequent flyer account if they’re an authorized user on your Amex MR card. Getting the PRG or any Amex charge card, generally, won’t have any bearing on your eligibility to get the Amex Hilton and SPG cards down the line. (Getting the PRG, which is a personal card, and any of Amex’s other personal charge or credit cards will count against your 5/24 status and could make you ineligible for some of Chase’s most lucrative cards that are subject to the 5/24 rule.) The Hilton and SPG cards earn points in their respective hotel loyalty programs. You can’t transfer Hilton points to much, but SPG’s Marriott points transfer to something like 60 airline partners if you’re not going to use them for hotel stays. Hilton and SPG/Marriott programs each have their own rules for transferring points between members, and to other programs.