Version 7 isn't that much different from 6 with regards to pan/crop and track motion. I don't believe you can upgrade to 6 now that 7 is shipping, so that probably answers which version you should upgrade to. Really, 6 has no advantages over 7 whatsoever so don't even bother considering it.

The only difference in pan/crop between version 4 and versions 6 & 7 is that Begin/End has been replaced by keyframes. This is actually a big improvement. Instead of being restricted to a single movement from the beginning to end of an event, you can now have multiple movements. If you want to start out simulating Begin/End from version 4, set the initial pan/crop parameters in the usual way. Look at the bottom of the pan/crop window and you'll see a small timeline. Click the 4th diamond shaped button beneath this timeline, the one with a right arrow that is touching a vertical line. This places the cursor at the end of the clip. Now set the ending pan/crop parameters just as if you had clicked the End button in version 4. It's that simple.

Now, on top of that, imagine if you wanted the pictures to move in and stop moving after 2 seconds, then stay still for the rest of the event. Simply move that little diamond that appeared on the small timeline from the end to the 2 second point. Now the movement will happen from 0 to 2 seconds and stop while the picture continues to show on the screen. You can set as many of these keyframe points as you wish to have the pictures move in multiple directions, zoom, stop zooming, etc. You'll find it's much better than a simple Begin/End.

And yes, you can get 2 or 3 pictures on the screen at once with version 4. Use Pan/Crop to zoom out by dragging the croppping rectangle out larger than the picture. This reduces the size of the picture in the frame. Add another picture on another track and zoom it out too. You can then move the cropping rectangle around to move each picture off center. If you move one to the right and the other to the left, they'll both be visible side by side in the frame.