This week, without any advance warning that I know of, Emirates became a partner of the US American Express Membership Rewards programme. View From The Wing did a good write up about it here.
As of the time of typing, there has been no announcement about Emirates joining the UK Membership Rewards programme. However, it might well happen.
Membership Rewards partners vary on a country by country basis – I think Miles & More is still a partner, for example, in Switzerland but nowhere else! However, it would be a little odd for Emirates to partner with the American programme but not with any others.
I have a personal interest here, as we are flying back from Dubai tomorrow on an Emirates A380 in business class. (I will review this flight next week.) To get the miles required, I had to transfer a chunk of Starwood Preferred Guest points to Emirates. It would have been far preferable to transfer American Express points instead, since SPG points are most valuable when used for Starwood hotels.
For now, there is nothing to do. It is something to keep in mind, though.
(PS. I know, before anyone mentions it, that Etihad is already a UK Amex partner, and that they cover similar ground to Emirates. However, Etihad very, very rarely offers more than two redemption seats per flight in Business or First, which makes it a no-go for me for family trips.)