As a temporary workaround, the following custom keyboard command provider can be used:

	public class CustomKeyboardCommandProvider : DefaultKeyboardCommandProvider
	{
		private GridViewDataControl parentGrid;

		public CustomKeyboardCommandProvider(GridViewDataControl grid)
		 : base(grid)
		{
			this.parentGrid = grid;
		}

		public override IEnumerable<ICommand> ProvideCommandsForKey(Key key)
		{
			List<ICommand> commandsToExecute = base.ProvideCommandsForKey(key).ToList();

			if (key == Key.Enter)
			{
				commandsToExecute.Clear();
				commandsToExecute.Add(RadGridViewCommands.CommitEdit);
				commandsToExecute.Add(RadGridViewCommands.BeginEdit);
				commandsToExecute.Add(RadGridViewCommands.MoveDown);
			}

			return commandsToExecute;
		}
	}

A possible workaround is to predefine the CellTemplate of the column as well.

Workaround: reused the cell element like this:
CreateCellElement(Telerik.Windows.Controls.GridView.GridViewCell cell, object dataItem)
{
    var button = cell.Content as Button;
    . . .
 
    return button;
}