Nope, nothing has changed! You can still MITM with BGP in the exact same manner! BGP is like SS7 -- once you get access to use it, it is wide open and completely insecure and no effort has been made to use it. All its security is predicated on the idea that anyone with access will have too much on the line to abuse it, and responsibility for monitoring announcements for your own IP is considered your own problem. Ask around -- how many people in your social circle of admins keep track of rogue announcements? How many would notice if this were going on?

More colocation facilities in the US and Europe now do prefix filtering at egress - but this matters little, as there are still quite enough that don't. In contrast, there's virtually no prefix filtering in Africa or Asia (remember when an accidental BGP announcement from Pakistan killed YouTube worldwide?)