There's a specific rule allowing the defendants to appeal immediately.
"APPEAL FROM INTERLOCUTORY ORDER. (a) A person may appeal from an interlocutory order of a district court, county court at law, statutory probate court, or county court that. . .denies a motion to dismiss filed under Section 27.003" Tex. Civ. Prac. & Rem. § 51.014(12).
It's the plaintiff who can't appeal automatically.
If the defendants are unhappy with the denial of the TCPA as to the defamation counts, they can appeal immediately.