Adding FW to any release does just exactly that. It adds some files to the TFTP directory. That has never been the way to add support for devices.
Support for devices is only achieved in 2 ways.
a) either it's supported natively in your version
b) you install a devpack
Table 1 Minimum Required Device Pack Version
http://www.cisco.com/en/US/partner/docs/voice_ip_comm/cuipph/7962g_7942g/firmware/8_3_2/english/release/notes/62832.html#wp42233
Since you'll be adding devpacks for new devices you'll need to to a cluster reboot as it's mandatory.
HTH
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HTH
java
if this helps, please rate