Canon has already announced the new EF 85mm f/1.4L IS USM lens last month, and is also rumored to announce EF 50mm f/1.4L IS USM lens in early 2018. According to CR, there could be also an EF 135mm IS USM lens to be announced in late 2018.
The old EF 135mm f/2L USM lens was released in April, 1996, 20 years old now. So this new rumored EF 135mm IS USM lens should be the replacement of EF 135mm f/2L USM lens.
via: CR