What would likely be gained or lost by choosing the FZ50 successor over the FZ28?
Before I answer, I must point out that the FZ50 successor that I'm implying is still a "rumor". Let me also apologize for such a long post, but it's 3:30am for me & I think my editing skills diminish considerably around the 3am mark...
So the facts are these, The FZ50 "ought" to have had an upgrade a long time ago, as its' two generations behind. Panasonic is (along with Olympus)
launching the micro four-thirds camera system. Panasonic has invited (in certain select markets only)
camera-journalists for the launch a scintillating new camera before Photonika. And finally Photonika is happening in September, and Panasonic & Olympus (either, or both)
need to have some form of a working model available for Photonika.
Now its all this (and a whole bunch of other rumors)
is what leads me & others to believe that there is going to be a micro four thirds successor to the FZ50.
Now why you should or shouldn't be waiting for this basically comes down to the same argument on why you should or shouldn't be getting a four-thirds dSLR (like the excellent E-420 by Olympus) instead of the FZ-28.
[Please note, personal opinions & biases may follow]
What the micro four thirds successor would allow, would be vastly improved IQ over the fz-28, at a cost of... well just "at a cost" should suffice.
You would need to invest heavily in lenses, and I can promise you that if Panasonic's dSLR record is any indication, the camera itself will cost a small fortune.
For me personally, the decision to go for the fz28 (or the bridge segment altogether)
was based on two factors...
First off, I wanted a camera that I could happily take with me wherever I went. Carrying a backpack full of lenses & converters & filters & a significantly large dSLR for a walk 'round the block just didn't allow me that sort of freedom. Secondly, I needed something that could allow me to grow in my appreciation & capability as a photographer without it costing an obscene amount of money that I would feel guilty over not recovering... (and getting hand-held stabilized lenses that would equal the 27mm-486mm range of the fz28 would indeed be an obscene amount for a hobby, IMO)
So while the micro four thirds potentially eliminates the first of my problems, I am rather certain it would multiply the second tenfold. I have seen many images from the fz28, along with earlier fz series cameras & other popular bridge cameras & I don't consider them too inferior to dSLR shots & a'least in developing my skill, I don't think I need a dSLR (full frame, standard, four thirds or micro four thirds)
*IF* Panasonic actually does release a micro four thirds for Photonika, it would be a first generation camera with little to no third party support or industry standard benchmarks to test its' mettle against. In 2-3 years, if I do still enjoy photography as much as I presume I would, then I would love to indulge myself with a 2nd or 3rd generation variant of the micro four thirds offering by Panasonic or Olympus (or even Leica, if some rumors are to be believed)
... but as it stands today, unless Panasonic launches a $500 micro four thirds with 27mm-200mm kit . . I won't be biting my words & regretting my decision.
I hope something in all the above managed to come across cohesively enough to help you Fred... If not, let me know I'll try to go through it again sometime in the morning.