The 3 month PS+ subscription will become more expensive in the UK going from £11.99 up to £14.99. I have no idea if this will affect other regions but it will not affect the yearly subscription as stated in the email.
Source: https://www.reddit.com/r/PS4/comments/3g14rw/anyone_in_the_uk_got_an_email_saying_the_ps_plus/
Edit: Apparently the price will also increase in New Zealand (from 24NZD to 32NZD) and in The Netherlands (Eurozone) as people are saying in the above Reddit post's comment section.
Edit: The price in France (and the entire Eurozone) will increase from €14.99 to €19.99 http://www.neogaf.com/forum/showthread.php?t=1091679