I believe the rumor that a new Canon 200mm IS & 800mm IS will be released, as soon as 2020.
These are the various reasons why it will happen then
1) Nikon's 200 VR2 & 800 VR are still at a disadvantage when it comes to lens weight to Canon. VR are now the same number of stops to Canon's IS. Only advantage of the Nikons are the the optical coating and the dedicated TC of the 800mm VR.
2) Both Canon lens were announced in 2007 and shipped 2008. These make both lens 5-6 years old. All the Series 1 super teles with IS were made obsolete by 2011 when the Series 2 super teles with IS were announced. That's a 12 year product cycle.
3) 200/1.8, the predecessor of the 200/2 IS, was announced in 1988 and discontinued in 2003. That's a good 15 years.
4. Here is a list of L lenses that need to be updated due to their lens age. All these lenses probably sell more volume in a week than either white primes in its whole production run.
1993 - EF 400mm f/5.6L USM
1993 - EF 1200mm f/5.6L USM
1995 - EF 70-200mm f/2.8L USM
1996 - EF200mm f/2.8L II USM
1996 - EF180mm f/3.5L Macro USM
1996 - EF 135mm f/2L USM
1997 - EF300mm f/4L IS USM
1998 - EF100-400mm f/4.5-5.6L IS USM
1998 - EF 35mm f/1.4L USM
1999 - EF 70-200mm f/4L USM
2003 - EF17-40mm f/4L USM
2004 - EF28-300mm f/3.5-5.6L IS USM
5. Here is a list of non-L EF lenses that need to be updated due to their lens age. All these lenses probably sell more volume in one day than either white primes in its whole production run.
1987 EF 135mm f/2.8 with Softfocus
1987 EF 50mm f/2.5 Compact Macro
1990 EF 50mm f/1.8 II
1991 TS-E45mm f/2.8
1991 TS-E90mm f/2.8
1991 EF 100mm f/2 USM
1992 EF 20mm f/2.8 USM
1992 EF 85mm f/1.8 USM
1993 EF 50mm f/1.4 USM
1995 EF 28 f/1.8 USM
6. As mentioned on 4 & 5 both lenses are not volume sellers. So whether they update this tomorrow or next decade they it wouldnt sell all that much.
I'd only upgrade if they can reduce the weight a further 25% or more and increase the f-number to say by 1/2 or a full stop.
Now, I could be wrong so dont bother reading this anymore.