Doubt it's to replace the 717 as they are at most around 15 years old which is basically brand new by Qantas standards.
Can I suggest you do some research?
Year of manufacture.... VH- NXH 1999 VH-NXE 2000 VH-NXI 1999 VH-NXD 2000 VH-YQY 1999 VH-YQX 1999
Which makes them OVER 18 years old, nearly nineteen.
Cobham already operates the E190 and have people with experience operating the type.
Cobham ceased E190 operations in February this year. That was also NJE not NJS, in other words a different business unit. Not to say that they will not get more of that type or even contract to Q. Also most of their Ejet pilots left the company.
Do QF own the B717's or Cobham?
They are owned by Qantas.