He's adorable! I remember when I adopted Coco, she was super sociable with her old owner but she was incredibly skittish when we brought her home; she did a complete 180 almost overnight. But thats only to be expected, because everything is new to them and they don't understand what's happening. It took me about 3 months to get her to really open up, and every day I still see improvements and now she's a total love-bug.
Sometimes it just doesn't work out. But I also wouldn't be discouraged if Mecki goes through behavioural changes as he quills; it can take a lot of work (often many months) to gain a hogs trust, and it wouldn't be completely unheard of to hear of some super friendly hogs become utter grumps as they age - but with a lot of work and patience, they can often (though not always) tame down again. I'm sure you're well aware of all this already, but just wanted to mention it just in case.