It is not easy to track the source of all the new forms, but I feel that the following people had major roles in their creation:

Li Tianji (李天驥) was one of the main masters chosen to create the 'simplified' forms of Taijiquan (太極拳), and he also created the first simplified Baguazhang (八卦掌) form taught as the standard form in the wushu academies, and was based on Sun Lutang's (孫祿堂) style. Li Tianji studied first with his father, Li Yulin (李玉琳) (student of Xingyiquan (形意拳) masters Hao Enguang (郝恩光) and Sun Lutang, and Yang family Taijiquan (楊氏太極拳) master Yang Chengfu (楊澄甫)), and later with Wudang Sword (武當劍) master general Li Jinglin (李景林). Men Huifeng (門惠豐) was probably another master involved in creating modern taijiquan. Bearers of the traditional styles like masters Yang Zhenduo (楊振鐸) (Yang Chengfu's third grandson), and Chen Zhenglei (陳正雷) and Chen Xiaowang (陳小旺) of the Chen Village (陳家溝) also probably affected modern traditional taijiquan. Chen Xiaowang today lives in Australia. Sun Lutang's daughter, Sun Jianyun (孫劍雲) probably helped in creating modern Sun style Taijiquan styles.

Modern Changquan (長拳) was probably created by Chaquan (查拳) master Zhang Wenguang (張文廣), Huaquan (華拳) master Cai Longyun (蔡龍雲), and others. Cai Longyun is famous for his victory in a public match with a Russian when he was still a young teenager; he won twice, once using kicks, and the other time using only punches.

Seven Star Praying Mantis (七星螳螂拳) master Yu Hai (Tiantang) (于海(天堂)) created most of the modern praying mantis forms; his student Qiu Pi Xian created another modern praying mantis form Tanglangxiaotao (螳螂小套). Yu Hai is famous for his roles in many Kung Fu movies alongside Jet Li (李連傑), often as the 'father figure' or 'senior monk' - who always seems to know praying mantis style.

Li Ziming (李子鳴), Sun Zhijun (孫志君), and Liu Jingru (劉敬儒) also probably affected modern baguazhang, especially the latter, who is still very active in teaching modern wushu students. Li Ziming was the head of the Beijing Baguazhang Research Association, the first single-style martial arts organization in China.

Shaolin Diamond Dhyana Ziranmen (少林金剛禪自然們) master and Buddhist monk Wang Xinde (王信得) probably passed down what would become the modern snake style form from his knowledge of traditional routines. He is currently living in Australia as the abbot of a Buddhist temple that he raised.

Bajiquan (八極拳), Fanziquan (翻子拳), Piguaquan (劈掛拳), and Tongbeiquan (通背拳) master Ma Xianda (馬賢達) and his brothers probably helped in creating modern Fanziquan, Tongbeiquan, Piguaquan, and Bajiquan styles.