If you travel out of USA, your change of status application from H4 to H1 will be rejected. As change of status means that you are living within USA and changing your status from H4>H1 without going out of USA for H1 stamping.
This will in anyway not affect your main H1B application. Once you come back into USA with your valid H4 visa and only once you get your H1 approved notice, you can apply for change of status again. Your change of status has to be approved in order to start a job (this option make take months, as there is no premium option for Change of status petitions), until then you are still on H4 and cannot work at all.
In case your H1B is approved when you are out of USA, you may use the approval notice and get H1B stamped at a US consulate, then enter the country to start job immediately.