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The sentence sounds O.K. to me. I'm not sure which element causes your doubts. Contractions are acceptable in informal English, so, assuming we know what the pronoun 'that' refers to (should be clear from the context), the sentence is correct.
As regards the usage of 'going to', we must remember that it is used not only as an expression of intention (chiefly with the first person) but also as 'prediction based on evidence'.
Example: you're watching a football match and your favourite team are playing exceptionally badly, then you may say 'Geez, playing like that they're surely going to lose...' (of course they have no intention of losing the game, but the opponent is just superior in all aspects).
All in all, I personally wouldn't question the correctness of your example, but let's wait for a native speaker to pop in with a reply.