We have a VC consisting of 2 x EX4200-48t and 2 x EX4500-40f.
What would be considered replacement hardware for this chassis.?
2x EX4300-48T + 2x EX4600-40F. 24 ports are SFP+, you will need 4x 40Gb->10Gb breakout cables or two 8-port expansion modules for the other 16.
2x EX4300-48T + 2x QFX5100-48S
If you are goiong the QFX5000 Series route vs EX4600, even though EX4600 and QFX5100 are the exact same hardware, difference is SW, I would suggest going with QFX5110 vs QFX5100 - has all plus more. If any product is nearing a point of becoming End of Sale, it would be QFX5100 as QFX5110 has been a better option for a long time, EXCEPT for QFX5100-48T. In 2020 when QFX5120-48T becomes an 10GBase-T option, then End of Sale of QFX5100 may occur sometime after.
OK, both suggestions are good, thanks both of you for replying
AFAIK you cannot VC EX4300's with QFX5110's.