They're supposed to come in Fall. I'm hoping for October they'll do the 3.0 update, and Box 15 will help Synchro strategies. Be excited for this; it's a cool mechanic that'll work with a variety of decks.
Synchros summon is interesting but may be a little powerful for new players from an experienced player's hand. And new players can easily form a desk using synchros without knowledge of dueling. These may be reasons why synchros still not available.
Synchros isn't powerful. They're need tuner and 1 or 2 monster on the field. We'll dont get SP summon tuners for first, we have to wait 1 turn to synchro summon. Tricky and other SP summon monsters are bad, because if we get lvl1 tuners first, you can do nothing. red-eyes deck with lvl1 tuners are good to summon Stardust dragon and Red dragon archfiend.
Synchros arent powerful. Some tuner are powerful. Handtraps. Ash blossom, White rabbit... (or effect veiler but it's not tuner) If someone has 3 of them it's will be very op. Some tuner can be SP summoned from GY.
Synchros aren't powerful? Lol. To some degree, that is true. None of the mechanics are inherently powerful. (In theory, Synchros, Xyz and Links should be roughly equal, taking similar resources.) But individual cards are. And Tuners are usually weaker cards than Synchros. Plaguespreader Zombie is not more powerful than Trishula. Probably not more powerful than something like Scarlight, even.
Synchro and xyz ruined the game I really hope duel links keeps them all out of the game and keeps it to the original Yu-Gi-Oh! Format so many people will fall off (including me) otherwise