Complex sentence: The Henney Kilowatt is already recognized as one of the great milestones of automotive history; however it is likely to gain in historical significance as electric-powered vehicles take on a more prominent role versus their traditional gas-powered counterparts.
Split into simpler sentences: The Henney Kilowatt is recognized as one of the great milestones of automotive history. The historical significance of the Henney Kilowatt is likely increase in the near future as electric-powered vehicles take on an even more prominent role versus their traditional gas-powered counterparts.