Q: Can you upgrade the AirPort card in a mid-2012 MacBook Pro?

Only the Mid 2013 MacBook Air is available with a 802.11ac card, so you can't get it onto the MacBook Pro. This doesn't mean that the AirPort card may not be replaceable, even if I doubt it.

You can buy a USB Wi-Fi adapter that supports 802.11ac, so it's the same as having a 802.11ac wireless card

You are welcome

Is there any point to buying a 802.11ac router if we are using a current MacBook Pro? 

If using a Ethernet connection, would there be a noticeable difference in speeds using a 802.11ac vice 802.11n? 

I need a new router and am trying to figure out if i should go for ac.

The answer is wrong.

Macbook air's ac card can swap into pro retina machine.

See: http://techctrlr.com/features/2013/7/3/it-works-so-why-is-80211ac-not-in-the-ret ina-macbook-pro

Hey - I don't think a USB adapter is the same thing. We might be able to make a replacement; check the following link out:

http://www.quickertek.com/products/QCard2.html

The ac module is called QCard 2. What do you guys think about it? I just asked a compatibility question on QuickerTek, Inc.'s facebook page.

I don't want to necro old threads, but this is the first thing that pops up in google, so I'll post it here for other people looking:

Tl;dr: yes

You can replace the card with airport card from newer macbook pros, and it will work just fine. There was some concern about antennas being capable of MIMO and beam forming, but wifi ac seems to work fine, here are results of iperf tests (first is just upload, second is simultaneous upload and download; using Linksys EA6400).