Update
Having reached out to our sources at Sony we've heard back that there are no plans to roll out a similar price rise here in Europe, at least not next month. Beyond that we don't know what Sony's plans are for PS Plus in territories outside of North America.
Original
Sony has just increased the cost of the PlayStation Plus subscription service in North America, with the new price coming into effect on September 22. Here's the announcement in full from the PlayStation Blog:
Starting on September 22, 2016, prices for PlayStation Plus memberships will change to $59.99 USD/ $69.99 CAD for twelve months (rising in the US from $49.99) and $24.99 USD/$29.99 CAD for three months (an $8 increase). The monthly plan will change to $11.99 CAD in Canada, and remain $9.99 USD in the U.S. If you are a current member, the new prices will take effect if your membership renews on or after this date.
PlayStation Plus strives to enrich your PlayStation experience through a world-class service built for our fans. This marks the first time that PS Plus membership prices will increase in the U.S. and Canada since the launch of the service in 2010. The new pricing reflects the current market conditions while enabling us to continue providing exceptional value to our members. As a member, you will continue to enjoy the benefits and features that enable shared experiences, such as online multiplayer, free games, and exclusive discounts. You will also continue to get exclusive benefits such as online game save storage and discounts across the PlayStation digital services.
If you do not wish to continue your subscription, please be sure to cancel it by turning off auto-renewal in your account settings before September 22, 2016.
We thank all of you, our PlayStation Plus members, for your ongoing support.
It remains to be seen whether a similar price hike is coming to European subscribers, and there's currently no announcement on the EU Blog. We'll keep our eyes and ears open and will update you as soon as we hear anything.