Rodman & Renshaw’s Ashok Kumar has issued a note to clients loaded with nuggets that, if true, would spell bad news for tablet computers.

• Supply chain checks that suggest that Apple’s (AAPL) monthly iPad production rate is unlikely to exceed 2 million per month by year’s end — considerably less than the 3 million/mos. some had predicted. That would put those 6+ million sales estimates for the December quarter at risk. “This shortfall will be the second quarter in a row,” he predicts.
• Unspecified “anecdotal evidence” that the MacBook Air is cannibalizing the iPad. “A fully functional notebook in a very attractive form factor,” he writes, “may be resonating more with consumers than a content consumption only device.”
• Trouble for the Google (GOOG) Android tablets: “Poor sell through of Galaxy has caused Samsung to dramatically revise down production volumes,” he says. “And on Dell’s Tablet, less said the better.”
• Delays for Research in Motion’s (RIMM) tablet: “PlayBook continues to face technical issues with integrating the QNX OS. Volume launch has been delayed and production forecasts continue to be ratcheted down.”

“We do not see Tablets go the way of netbooks or a flash in the pan,” he concludes “But if current trends continue, the Tablet market may not end as much more than iPads or a tweener product between smart phones and next generation thin-and-light notebooks a la MacBook Air.”

Take all this with more than the usual grain of salt. For a sobering review of Kumar’s track record, see Daring Fireball here.

[Follow Philip Elmer-DeWitt on Twitter @philiped]