Essentialy I do need it for work and video editing .. I just hate to spend that kind of money and have them totally switch the game up on us .
What is actually known is this:
1. In the past, the iMac has typically been updated every 12 months or so.
2. The current iMac hasn't been updated since June 2017
(On the other hand, the Mac Mini just got updated after 4 years and the Mac Pro is 5 years and counting, and I believe it was about 3 years for the MacBook Air, one of Apple's most popular Macs. On the other hand, the 2018 MacBook Pro got "updated" with new graphics options after just a few months)
3. The typical dates for new Mac launches are June/July (Apple's WWDC conference), October and sometimes March
(oh, and there's usually an iPhone/Music/Services-only event in September, before which the MacRumors community always gets lathered up about new Macs and then acts all surprised when it turns out to be iPhone/Music/Services-only).
4. Anything else is speculation. Sometimes, there's a genuine leak (pictures of a case, registering a new device with the Wakkanda communications commission, clues from an OS update) but otherwise its just guessing.
So, really, the best you can say is that it would be
unsurprising if Apple launched an updated iMac in the next 6 months.
As for the speculation:
if Apple release a straight update of the iMac with 'like-for-like' updates of the components, apart from any improvement in the GPU, the most significant likely improvement is that the latest Intel chips have increased the number of cores across the board, so the i5/i7 iMacs would get 6 cores rather than 4. If you're doing multi-core intensive work like video or audio then that would be the most useful speed increas we've seen for a few years... but note the
if - Apple could just as well decide to go for lower-powered 4 core processors in the iMac to leave a niche for the pro models.
Always bear in mind that if Apple do re-design the iMac, you may or may not like the result. The easily-upgradeable RAM and the SD card slot are likely casualties of any major re-design. The price could easily rise.
On the other hand, the 2017 model is well-proven and you know what you are getting and will be a
big step up from your 2009 MBP.
So, to re-iterate what others have said - if you need a new computer for work
now get what is available - its not going to crumble to dust if a new version comes out next month. If you already have a system that is getting the job done, and just hanker after that new computer smell, wait.
...and if you always want to be able to get a new system in the form factor and hardware features of your choice with this year's CPU and GPU, switch to Windows or Linux.