Yeah - my fix comment was tongue in cheek. As I said, I just don't see the change as that big a deal - to be honest I didn't even notice it, and I use Sonar at least  8 hours a day. I do on the other hand fully understand that you do see it as a big deal.  Not much else I can offer sorry. You could submit a feature request.

I have filed a problem report, and submitted an email directly to Cakewalk support.
 
Again, if NO notes are selected, then wouldn't it be better to show ALL velocities rather than NO velocities?  If not, can you please explain?

I hear you - there really is no alternate explanation other than if you choose to show velocities on selected notes only that is EXACTLY what it does! No selected notes = no velocities.

Tripecac
I have filed a problem report, and submitted an email directly to Cakewalk support.

In this case a problem report may not be the appropriate action. The program appears to work as documented, however; there is a desire for an alternate behavior. This would be a feature request.

I understand that a literal interpretation of the label "Show Velocity on Selected Notes only" option would mean that we should not show any velocities when no notes are selected.  However, "Show Velocity on Selected Notes only" is only a label, and can be regarded as shorthand for the actual behavior. 
 
Check out the Sonar X2 documentation:
https://www.cakewalk.com/Documentation?product=SONAR%20X2&language=3&help=EditingMIDI.17.html

It says this:

SONAR has an option to show velocities for selected Note events. This option makes it easier to see and edit velocities when many Note events are present. It also makes it easier to change the velocity for individual Note events that are stacked (such as chords).
 
If there is no selection, velocities are shown for all Note events.

 
As you can see, as of X2, the feature was deliberately designed to show all notes when there is no selection.
 
This behavior is broken in Sonar Platinum.

Here is the current online documentation for the feature:
 
https://www.cakewalk.com/Documentation?product=SONAR&language=3&help=EditingMIDI.17.html
 

Show velocity on selected notes (optional)
 
SONAR has an option to show velocities for selected Note events. This option makes it easier to see and edit velocities when many Note events are present. It also makes it easier to change the velocity for individual Note events that are stacked (such as chords).

If there is no selection, velocities are shown for all Note events.

To only show velocity for selected note events
Click the Piano Roll view Notes menu and choose Show Velocity on Selected Notes Only.
The state of the Show Velocity on Selected Notes option is saved with the project, and the setting is separate for the Piano Roll view and Inline Piano Roll.

So yes, this clearly appears to be a bug.
 

OK. So either, the documentation needs to be updated or the program needs to be brought into alignment with the documentation.  If you have filed a report with Cakewalk, until they take action you will need to toggle the setting to suit your situation.

This bug is still present in Sonar 2016.05.
 
I have not heard back from any Cakewalk staff about it.

This is continuing to plague me in 2016.05, even with the recent update.
 
Are you able to see this bug report (from 22 April):
 
https://www.cakewalk.com/Support/Contact/Problem-Report-Status/49791
 
How long can we expect it to stay in New status?

Haha - Plagued is a strong word! As Scook pointed out this could well be intended behaviour as it is no less functional despite being different from how it worked previously. They may just update the documentation.