Since they have been calling each other and are already aware of each other's presence, you can place both cages on the same room to give your budgies the chance to be properly introduced.
The way your budgies will react and how the bond you have with them will be affected will entirely depend on the type and strength of the bond you have with them and also on your budgies overall personalities.
When the bond is strong and truly solidified (and this comes with the continued work and daily time spend with your budgies, the longer the time frame, the better), the changes in the bond will be lesser.
Even for the sweetest bird that came to us practically tame and friendly, if a new same species friend is added within just a couple of months, the bond with us is bound to suffer some changes and you may reach a plateau when it comes to further taming. Budgies will naturally bond more closely to each other especially when given the chance to share the same cage.
However, when given more time for the bond to strengthen (6 to 8 months), chances are higher the bond with us will not be as affected.
All of these aspects will of course depend mainly on the budgie's personality and the way he/she reacts to the presence of a same species companion.
It's not realistic to think nothing will change after adding a second bird, the dynamics are bound to change but this doesn't necessarily mean you will completely lose the bond with your budgies after introducing them to each other.
Continued work with both of them is needed to have the best results as far as taming goes.
You may even get the advantage to make better progress with your least tamed budgie with the help of your most tamed budgie.
You will be better able to make decision depending on your budgies behaviours when interacting more closely, this is for out of cage time or even to possibly house them together on the same cage.
What's more important is your budgies overall welfare and happiness.