What's important it the wording used; they would talk about a "focus" ("Torn-T is focused on Speed and defenses wow") the Therians had, while these MegaPokémon have an "increase". I don't think we're getting a new stat distribution, but a pure, bland increase on the mentioned stats, even if they still aren't the highest stat.
Say, Mawile's stats are 50/85/85/55/55/50=380; MegaMawile's said to have its defenses "sharply raised", so I'd bet on 50/85/115/55/95/50=450. As much as I'd love a Attack-Speed swap, I feel they aren't going to do it; they want the pokémon to reveal its unfulfilled potential, so they aren't going to give it any drawbacks besides the Mega Stone's requirements. So a, say, MegaScizor would only work if it got something BETTER than Techician.