Yeah, I first read something about this rumor just a day or so after Jeff Hardy showed up at TNA on the 4th. The way I look at it, it couldn't really hurt their careers to jump ship to TNA. They're not really doing much of anything in the WWE and really haven't been for quite a while.
However, if they were to jump ship to TNA, I can't say that I think it would hurt the WWE in any way, shape or form. Matt Hardy is someone that just does not have that x-factor that his brother Jeff has. Matt Hardy is a solid in-ring worker but he can be dull as shit to watch in matches sometimes. In the WWE, the only time Matt Hardy has been interesting is when he's done something with his brother Jeff, whether it be in a feud or as a tag team. As a singles wrestler, Matt Hardy has had runs with every championship in the WWE except for a world title and, quite frankly, none of Hardy's runs with any title he's held as a singles wrestler has been memorable in the least.
As for Gregory Helms, it's more or less the same. He's a good overall in-ring worker, but there's just nothing spectacular about the guy. In May 2007, Helms was put out of action due to having a couple of broken vertebrae in his neck, one of which was pressing against his spinal cord. Helms was completely MIA from the WWE until September 2008 when he started his interviewer thing with the WWE and didn't wrestle until December '08. So, Helms was gone for roughly a year and a half all told from WWE tv, which leads me to believe that some of the higher ups in WWE must really like Helms. To be honest, I'm surprised that the WWE did keep him on the payroll with him unable to work for so long. If he did jump ship, part of me would think it's a pretty shitty thing to do because it doesn't really show much loyalty for a company that stood by him when he was on the shelf for so long.