15 yr to 30 yr loan on primary residence

[Daniel Pak]

Currently I have a big fat mortgage on my primary residence (about 4k a month) , refinanced last year at a good rate of 3.125%.  However, wondering if it was better to refinance to a 30 year to a 4.5% rate, i willl save more money monthly (about 1.2k a month) to invest in rental properties.  Do you guys think its wise to refinance to a worse rate, or better to just keep my 15 year at the good rates. Are there any other options? Unfortunately I am not able to sell the house because my wife is extremely attached to this house.  Do you guys think the mortgage rates will continue to rise during the next fear years?  With my current income we are able to save about 1k a month after all expenses, but i feel like saving more will speed up our real estate portfolio.  I am really considering to switching to a 30 year, but dont want to to regret it and lose my good rate, would love to hear your guys input and advice on this matter!