"Probably" no - RAW, it would change from Range: Touch to Range: Close, but the actual effect would still end if the target went beyond close range.
I could definitely see a GM ruling that it would increase everything by one step, for example allowing you and the target to cast Range: Close spells on each other so long as you were withing Range: Medium from each other... of course, that would require putting Reach on all your CLW and such, but might be worth it.
If your GM is very lenient it would probably work like you seem to hope, allowing Range: Touch spells to be extended to Range: Medium.
I don't think it'd be that much of a balance issue either way.
Sacred Bond lets you cast spells with a range of touch on your partner so long as she is within close range. It only works with touch spells. If you were to change the range of a spell to something other than touch (such as with Reach Spell) it would no longer have a range of touch and, therefore, no longer have any interaction with Sacred Bond.
So, you can't combine Sacred Bond and Reach Spell to cast touch spells at medium range.