According to "The People's Religion", from the Gallup organization,
here are changes in percent of U.S. Population

	Bapt.  Methodist     Presby.	      Catholic
		      Lutheran	      Episc.  
87	20	9	6	3	2	28
80	19	10	6	4	2	28
69	20	14	7	6	3	26
67	21	14	7	6	3	25

The fastest growing groups seem to be evangelical churches.  From
1973 to 1983:
  S. Baptist: 		 12.2M to 14.1M, +15%
  Mormons:      	  2.6M to  3.6M  +40%
  Assemblies of God:      1.1M to  1.9M  +71%
  7th Day Advent:         464K to  624K  +34%
  Church of Nazarene:     418K to  508K  +22%

What's worse for the "mainline" churches is the percentage of 
young adults, assuming this indicates the future:

  church	total   18-29

  Catholic	28	31
  none		 9	13
  Baptist	20      21
  Methodist	 9	 6
  Lutheran	 6	 4
  Episcopal	 2	 1
  Presbyterian	 4	 2
  UCC		 2	 1
  Christian	 2	 2

Gallup, and others I've seen predict a continuing contraction of the
"mainline" churches, and growth in both Catholics and evangelicals,
including Mormons.