According to ZOS_Brianwheeler our existing weapons will not be upgraded.
https://forums.elderscrollsonline.com/en/discussion/comment/6709784#Comment_6709784
Dragonstar Arena and Maelstrom Arena proposed weapon changes from PTS 6.0.0:
Dragonstar Arena
Caustic Arrow:
This set now grants up to 330 Weapon Damage against targets affected with your Poison Arrow, up from 300.
This set now has a perfected version that grants up to 103 Weapon Damage.
Destructive Impact:
This set now grants up to 600 Spell Damage for 4 seconds after casting Destructive Touch.
Reduced the cost reduction granted towards Destructive Touch to 10%, down from 30%.
This set now has a Perfected version that grants up to 103 Spell Damage.
Grand Rejuvenation:
This set now grants up to 117 Magicka and Stamina to target affected, up from 100.
This set now has a Perfected version that grants up to 877 Max Magicka.
Puncturing Remedy:
Increased the healing granted by this set to 6130, up from 2500.
Increased the duration of the armor bonus to 5 seconds, up from 3.
The armor granted from this set will now incorporate over healing into its calculation, ensuring it will always grant a benefit when engaged with.
This set now has a Perfected version that grants up to 3% Healing Taken.
Stinging Slashes:
This set now increases any instance of damage done with Twin Slashes by 2102, rather than only increasing the bleed damage by 1600.
This set now has a Perfected version which grants up to 666 Weapon Critical Rating.
Titanic Cleave:
Increased the stacking damage bonus of this set to 1550, up from 1500.
Increased the target cap to 24, up from 6.
Note we will closely monitor how frequently this allows utter devastation to large groups and will address it appropriately so it is similar in function to Proximity Detonation.
This set now has a Perfected version which grants up to 1190 Physical Penetration.
Maelstrom Arena
Cruel Flurry:
Increased the Weapon and Spell Damage granted from this set to 1690, up from 1000.
This set now has a Perfected version which also grants up to 103 Weapon Damage.
Crushing Wall:
Increased the damage bonus of this set to 1353, up from 1341.
This set now has a Perfected version which grants up to 1190 Spell Penetration.
Merciless Charge:
Increased the damage done by this set to 10032 over its duration, up from 7200. The damage done is now once again labeled as a Bleed.
This set now has a Perfected version which also grants up to 1190 Physical Penetration.
Precise Regeneration:
Decreased the Magicka granted from this set to 500, down from 800.
Removed the cooldown from this set, though note it cannot proc from the event of simultaneous critical heals from Radiant Regeneration.
This set now has a Perfected version that grants up to 666 Spell Critical Rating.
Rampaging Slash:
Decreased the Magicka and Stamina restore from this set to 1904, down from 2000.
This set now has a Perfected version which also grants up to 77 Magicka and Stamina Recovery.
Thunderous Volley:
This set now increases the damage done of your Volley by 430 and increases by 143 per tick, up from 320 and increasing by 110 per tick.
This set now stacks up to a maximum of 8 times, rather than continuously stacking.
This set now has a Perfected version which grants up to 666 Weapon Critical rating.
[EDIT: Added PTS proposed weapon adjustments for perfected and non-perfected vDSA and vMA weapons]