The title nutshells the news pretty well, actually.
In Autumn, SWtOR is going free-to-play, with a variation of the model that’s been successful for a bunch of other MMOGs.
Of course, the end times is being predicted by vocal members of the playerbase, so I’ll answer to that a little in another post.

To summarise the F2P model, the initial price of the game is being dropped to $14.99, with one month of free subscription.
Considering the common practice of currency conversions, this will likely equate to £14.99, €14.99, and 14.99 in any other currency that’s stronger than the USD.
Then, you’re in.
From there, once your first month’s up, you can either continue with a monthly subscription for full access (including a stipend Cartel Coins (Real-Money shop currency)), or you can play with limited access for free, with the ability to remove some limitations with Cartel Coins (which you can buy for real money).
For more information, you have:

The official information page;
The option/feature chart;
The official FAQ;